Tsubasa Reservoir Chronicle Vol 1

Tsubasa: Reservoir Chronicle by CLAMP. An Adventure manga rated Teen, published in English by Kodansha.

When Princess Sakura's memories are scattered across other worlds in the form of feathers, her childhood friend Syaoran sets out to recover them. Joined by a wandering ninja and a mysterious magician, he journeys through dimensions, though the price of his quest is that Sakura will never remember their past together.